Sea breeze

About: Sea breeze is a research topic. Over the lifetime, 2544 publications have been published within this topic receiving 55651 citations.

Weibull distribution of bora and sirocco winds in the northern Adriatic Sea

Abstract: Wind data measured at three off-shore stations in the northern part of the Adriatic Sea were considered: the Coastal oceanographic station Piran buoy (COSP), the PALOMA tower (the Gulf of Trieste) and the A. ALTA platform (Venice). Annual wind roses for all stations and additional seasonal wind roses for COSP are presented. The Weibull distribution function was applied to wind speed frequency distribution for winds from all directions and separately for bora and sirocco winds. Wind speed frequency distributions for bora winds measured at COSP and PALOMA are bimodal. One peak of this distribution of speeds belongs to nocturnal land breezes and another to bora winds. The peak separation method based on the difference in potential temperature of the atmospheric boundary layer (ABL) between two land stations (Udine and Zagreb) enabled the successful separation of the peaks of bora and land breeze winds. The frequency distribution of the wind speeds changed to the usual unimodal distribution when only those episodes were considered in which the potential temperature of ABL above Udine is higher than that above Zagreb.

Statistical analysis of boundary layer heights in a suburban environment

Abstract: The atmospheric boundary layer (ABL) is characterized by the turbulence eddies that transport heat, momentum, gaseous constituents and particulate matter from Earth’s surface to the atmosphere and vice versa. Thus, the determination of its height has a great importance in a wide range of applications like air quality forecasting and management. This study aims at estimating the height of the ABL in a suburban environment and at investigating its temporal variation and its relationship with meteorological variables, like temperature and wind. For this purpose, radiosonde data from the suburban area of Thessaloniki, Greece, are analyzed. The data analysis reveals that ABL height is usually below 200 m in the morning hours during all seasons of the year and that is also low when near-surface temperature and wind speed are low too. Additionally, noon ABL height exhibits a strong seasonal variation, reaching higher values during summer than during winter.Very high values of ABL height, of the order of ~3,000 m, are occasionally observed in Thessaloniki during summer. Moreover, sea breeze development during summer is related to a slight reduction of the ABL height.

Inter-annual variability in the temperature of the North Sea

Abstract: A numerical model is formulated to study inter-annual variability in the temperatures of the North Sea. Vertical diffusion is simulated using a simplified semi-analytical approach. Sensitivity tests examine the impact of changes in wind speed and air temperature, including specific anomalies observed during the 15-month survey period of the U.K. North Sea Project. In the North Sea, the sea surface temperature closely follows the air temperature, with a mean 1-2°C above the latter. Their seasonal amplitudes are closely similar in shallow water, but the sea surface amplitude is somewhat reduced in deeper water. Any increase in wind speed forces the sea surface temperature to converge even more closely towards the ambient air temperature. Beneath the surface, increasing depths both delay and attenuate surface variability—a process reinforced by thermal stratification that exists between March and October in deeper waters. Anomalies in observed sea surface temperatures can generally be directly related to concurrent air temperature anomalies with an indirect influence of anomalous wind conditions. However, air temperature anomalies are reduced in amplitude in their impact on depth-averaged sea temperatures because of the attenuating effect of water depth. Model simulations emphasise the essentially localised nature of the air-sea thermal balance in the central North Sea, with only a secondary effect of horizontal advection and dispersion. Any changes in mean temperature along the Atlantic boundary will have little influence on the more enclosed regions of the North Sea. Moreover, the effect of corresponding changes in the annual cycle will be reduced even further. Throughout this study, feedback effects of water temperature onto ambient air temperatures have not been considered. Future studies will need to incorporate this mechanism.

Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source

Abstract: . In situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001- Dec 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March - mid October) and 1.8+0.8 pptv (December-February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms-1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ΔCHCl3/ΔCHBr3 varied strongly according to the prevailing wind direction; from 0.60+0.15 in south-easterly (100-170° and northerly (340-20°) air to 2.5+0.4 in north-easterly (40-70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however had an immediate fetch inland, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the north-easterly land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 20.4(0.4-948) Gg yr-1, which is approximately 7% of the total global source.